Transitions to asexuality and evolution of gene expression in Artemia brine shrimp.

Ann Kathrin Huylmans,Francisco Hontoria,Beatriz Vicoso,Ariana Macon

doi:10.1098/rspb.2021.1720

Abstract

While sexual reproduction is widespread among many taxa, asexual lineages have repeatedly evolved from sexual ancestors. Despite extensive research on the evolution of sex, it is still unclear whether this switch represents a major transition requiring major molecular reorganization, and how convergent the changes involved are. In this study, we investigated the phylogenetic relationship and patterns of gene expression of sexual and asexual lineages of Eurasian Artemia brine shrimp, to assess how gene expression patterns are affected by the transition to asexuality. We find only a few genes that are consistently associated with the evolution of asexuality, suggesting that this shift may not require an extensive overhauling of the meiotic machinery. While genes with sex-biased expression have high rates of expression divergence within Eurasian Artemia, neither female- nor male-biased genes appear to show unusual evolutionary patterns after sexuality is lost, contrary to theoretical expectations.

Highlights

Sex is nearly ubiquitous in animals, despite the costs associated with sexual reproduction
The phylogenetic relationship between the six Eurasian Artemia lineages used in this analysis was first established based only on mitochondrial data and two nuclear genes [33], which had suggested the existence of independent asexual lineages, including one more closely related to A. sp
We find more differentially expressed genes with increasing phylogenetic distance, but again only a small proportion of differentially expressed genes are shared between the three asexual lineages

Summary

Introduction

Sex is nearly ubiquitous in animals, despite the costs associated with sexual reproduction. Asexual populations often have similar diversity, rates of adaptation and numbers of transposable elements as their sexual relatives [11,13,18,19,20,21,22] It is, still unclear whether shifts to asexuality consistently bring the changes in fitness that are predicted by theory. The relationship between sexual and asexual lineages, and how diverged they are, are still questions under debate, which have mostly been investigated using a small number of mitochondrial and nuclear sequences [32,34,37] How different these species and populations are at the gene expression level, and whether the asexual lineages share a single reproductive programme (as expected under contagious parthenogenesis), is still unknown. We characterize patterns of expression in males and females of sexual species, and compare them to expression patterns found in asexual females, allowing us to test whether a core set of genes changes consistently with the evolution of asexuality and whether we can detect a feminization in expression patterns in asexual females, consistent with a release from sexual antagonism

Results

Aibi Lake

Discussion

Methods

Findings

18. Ollivier M et al 2012 Comparison of gene